US2725290A - Development of multi-layer color films with developers containing mercapto azoles - Google Patents

Description

Edward A. Smith, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application November 14, 1951, Serial No. 256,369

1 Claim. (Cl. 95-2) This application relates to photography and particularly to the processing of multi-layer color films or papers.

In multi-layer photographic elements used for color photography there are usually three differently sensitive emulsion layers coated on one side of a single support. These emulsion layers may contain color couplers for the formation of colored images in the emulsion layers by development with a primary aromatic amino developing agent. One of the difficulties encountered in the development of such multi-layer elements, especially when the development is carried out at high temperatures, is the over-development of the top emulsion layer before the bottom layer is fully developed. This overdevelopment of the top layer is caused by the high rate 'of developer diffusion, developer exhaustion, gelatin swelling within the film, etc. It is obviously a disadvantage since each of the layers of the multi-layer element should be developed at about the same rate or during the same period of time.

It is, therefore, an object of the present invention to provide a method for preventing the overdevelopment of the top layer of a multi-layer photographic element. A further object is to provide a novel method for developing color images of uniform characteristics in a multi-layer photographic element. A still further object is to provide a method for permitting high temperature development of multi-layer color elements. Other objects will be apparent from the following description of my invention.

These objects are accomplished by color developing the exposed photographic element with a solution of a primary aromatic amino developing agent containing an azole having a mercapto substituent. This agent acts as an anti-foggant and diffuses more slowly than the other de- .veloper constituents, or varies in etfectiveness with depth of penetration because of the insolubility of the silver salt of the anti-foggant, and thereby reduces or prevents overdevelopment of the top layer before the bottom layer is fully developed.

Mercapto azoles which I have found useful for this purpose are l-phenyl-S-mercapto tetrazole, 4-phenyl-2-mercapto thiazole, Z-mercapto benzoxazole, 2-mercapto benzothiazole, and 1-2-napthyl-5-mercapto tetrazole. Other anti-foggants such as benzotriazole may be present in the developer solution.

According to my invention a multi-layer photographic element of the type described in Mannes and Godowsky U. S. Patent 2,304,940 or Jelley and Vittum U. S. Patent 2,322,027 is used as the multi-layer sensitive material. The sensitive elements of this type comprise a support of cellulose ester, paper or other suitable base having coated thereon a red-sensitive emulsion layer containing a magenta-forming coupler and a blue-sensitive emulsion layer containing a yellow-forming coupler. The couplers may be nited States Patent O minute.

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2 of the composition and incorporated in the manner described in Mannes and Godowsky U. S. Patent 2,304,940 .or Jelley and Vittum U. S. Patent 2,322,027.

Obviously the multi-layer element may contain two or more sensitive emulsion layers and may also have filter interlayers, subbing layers, backing layers and overcoating layers applied in the well known manner. One or more of the emulsion layers may also be free of incorporated couplers, the coupler or couplers for these layers being contained in the color developing solution.

While the exposed multi-layer elements may be processed at temperatures normally used in the processing of photographic films, my invention is especially useful for high temperature processing as, for example, processing at temperatures of about F.

The exposed multi-layer element of the type referred to above is processed according to my invention by development directly after exposure in a color developing solution containing the mercapto azole followed by the usual fixing and silver removal steps. The following example illustrates my invention.

' A multi-layer photographic element having three superposed emulsion layers of the type described in Jelley and Vittum U. S. Patent 2,322,027 was exposed to an image Water to 1 liter.

The time of development will depend on the nature of the particular silver halide emulsions employed by me, for example, development time may be of the order of 1 Development is followed by treatment in an acid hardening fixing bath and a silver removal bath according to well known practices.

The amount of anti-foggant used according to my invention may vary from 0.05 gram to 0.5 gram per liter of developer solution. Development may be carried out at temperatures up to about F.

It will be understood that the modifications and examples included herein are illustrative only and that my invention is to be taken as limited only by the scope of the appended claim.

What I claim is:

The method of preventing overdevelopment of the top emulsion layer of a multi-layer photographic color element having a red-sensitive emulsion layer containing a cyan-forming coupler, a green-sensitive emulsion layer containing a magenta-forming coupler and a blue-sensitive emulsion layer containing a yellow-forming coupler, which comprises exposing said element and developing it directly to colored images at about 130 F. with a solution of a primary aromatic amino developing agent containing 0.1 gram per liter of developing solution of 1- phenyl-S-mercapto tetrazole.

References Cited in the file of this patent UNITED STATES PATENTS 2,159,600 Murray et al. May 23, 1939 2,476,541 Friedman July 19, 1949 2,553,498 Duerr May 15, 1951